Compute the ratio of the rate of heat loss through a single-pane window with are

Question

Compute the ratio of the rate of heat loss through a single-pane window with area 0.15 m2 to that for a double-pane window with the same area. The glass of a single pane is 4.4mm thick, and the air space between the two panes of the double-pane window is 7.10mm thick. The glass has thermal conductivity 0.80 W/m*K. The air films on the room and outdoor surfaces of either window have a combined thermal resistance of 0.15 m2 K/W. Express your answer using two significant figures.
Compute the ratio of the rate of heat loss through a single-pane window with area 0.15 m2 to that for a double-pane window with the same area. The glass of a single pane is 4.4mm thick, and the air space between the two panes of the double-pane window is 7.10mm thick. The glass has thermal conductivity 0.80 W/m*K. The air films on the room and outdoor surfaces of either window have a combined thermal resistance of 0.15 m2 K/W. Express your answer using two significant figures.

Explanation / Answer

The ratio will be inverse of the ratio of the total thermal resistance.With two panes of glass with the air trapped in between,compared to the single-pane, the ratio of the heat flows is

Ratio =[2(L_glass/K_glass)+Ro+(L_air/K_air)]/[(L_glass/K_glass)+Ro]

Ratio =[2(4.4*10^-3/0.8)+0.15+(7.1*10^-3/0.024][(4.4*10^-3/0.8)+0.15]

Ratio =2.94

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